In recent years, the elements, devices, modules, apparatuses or instruments for detecting interactive gestures, postures or 3D scanning trajectories have been increasingly developed. For example, an infrared (IR) structured light can be employed to achieve the above detecting function. In the meantime, a planar scanning structured light is also preferred to employ in recognizing the interactive actions or the important indicating objects. In practical implementation, a collimating beam is required in the generation mechanism to make such a structured light. As a result, a collimated infrared light is necessary to achieve this function. However, since the current light source module with the function of generating the collimated light has bulky volume, this light source module cannot meet the requirements of the modern slim type mobile phone, wearable devices, and so on.
On the other hand, the current light source module is usually equipped with a dust-proof lens at a side of a housing thereof. The dust-proof lens can increase the resistance of the light source to the harsh environment and enhance the stability of the light source. The material of the dust-proof lens is typically a glass plate. In some situations, the dust-proof lens may be omitted or integrated into other part. However, if the dust-proof lens is omitted, the optical path length or the working distance is possibly changed. The change of the optical path length or the working distance may adversely affect the operation of the light source module, i.e., the effective back focal length is changed and the collimating property is varied. Therefore, it is important to develop a lens which is capable to work well both with/or without the dust-proof lens and install it in a compact-size and user-friendly apparatus of structured light generation in a mobile phone so as to extract 3D information or achieve the 3D gesture or scanning function.